The Biosand Filter

The Biosand filter in action

The sand filters I’m working with here are known as Biosand filters. They could more specifically be described as intermittently operated slow sand filters. The idea behind this technology was developed at the University of Calgary in the early 1990’s as a way of adapting continuous slow sand filtration (used somewhat extensively to treat municipal drinking water in Europe) to be used on a household level. The filters were developed particularly to meet the needs of people living in the rural areas of developing countries. In these areas, centralized water treatment and distribution systems are obviously highly impractical, and will probably remain as such for many years to come. Another fact, which is maybe equally obvious, is that these people living without access to treated water must still be drinking something every day. People die every day from drinking this untreated water. Nearly one in five children in Uganda will die before the age of five from diarrhea caused by drinking unsafe water. Even in the United States, dysentery was a leading cause of death as recently as 100 years ago. For close to 1 billion people, this is still the case.

That’s the depressing information, but here’s something to smile about: the Biosand filter removes 97% of bacteria, over 99.9% of viruses and effectively 100% of parasites from raw waters. In developing communities, the primary water treatment concern is removing these three types of waterborne pathogens. Not only are these filters effective, they are easy to build, use, and maintain. The filters can be constructed and maintained by the local people using only locally available materials. The only cost of the filters is the upfront cost of materials and labor. There are no operation or maintenance costs, and the filters can last for years. Biosand filters introduced in Nicaragua were found to still be functioning in excellent conditions after eight years. For the people drinking dirty water everyday, the ability for them to treat their own water in their own homes would invaluable, and the potential for the Biosand filter to provide to this ability is enormous.

The goal of my project is to introduce at least four Biosand filters in Makooma Community. Hopefully, this introduction will stimulate much interest in the filters. I’m applying for a grant to fund the construction of these four filters including the manufacture of the steel formwork needed to cast the concrete filter cases. Once this formwork is obtained, many filters may be constructed with the only expense being a small amount of concrete, sand, and gravel.

I now have only five weeks left with Busoga Trust, so the remainder of my time is going to be quite busy with the construction of these four filters after my grant proposal is accepted for funding. I’ll probably be spending much time in the field, in Makooma, which I’m very excited about. During my previous two visits to this community, I got to spend a little time with some of the cutest kids I’ve ever seen. They shared jyak fruit with me and we chewed on sugar cane, ruminating on possible solutions to their water quality problems.

On a side note: during my most recent visit to Makooma, I saw a fisherman carting the biggest fish I’ve ever off to the market on the back of his bicycle. It was a Nile Perch, fresh from Lake Victoria, and must have been close to 5 feet long!